"Theory of autism"--why Asperger's had to go

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Whereas the phenomenological similarities between Asperger's and developmental right hemisphere dysfunction have been alluded to in the literature (Molina, Ruata & Soler, 1986; Tsai, 1992), NLD has been a relatively unknown concept among psychiatrists (Klin, 1994). The importance of the NLD and related concepts lies in the fact that the neuropsychological profile obtained for individuals so described exhibits a greater right hemisphere dysfunction (Rourke, 1989), whereas the typical neuropsychological profile obtained for individuals with HFA indicates a greater left hemisphere dysfunction (Dawson, 1983; Rumsey, 1992). This would suggest that, based on neuropsychological profiles, there might be at least two types of conditions at the higher end of the spectrum of severe social disabilities: one type with predominantly left hemisphere involvement and the other with right hemisphere involvement (Tsai, 1992). The phenomenological similarities between Asperger's and NLD suggest the NLD profile as a neuropsychological model of Asperger's.

Abstract: The primary aim of this investigation was to assess to what extent Rourke's (1989, 1995) nonverbal learning disabilities syndrome (NLD) model resembles the pattern of assets and deficits seen in people with Asperger syndrome (AS). NLD can be characterized by a cluster of deficits primarily affecting nonverbal aspects of functioning, in the presence of proficiency in single word reading and a superior verbal memory. The neurological underpinnings of this syndrome may be dysfunction of white matter affecting right hemisphere functioning and interhemispheric communication. To explore this hypothesis, eight participants with AS (ages 10 to 41 years) were assessed in the following areas: the pragmatics of language and communication, verbal and visual memory, visual-spatial abilities, and bimanual motor skills. Results confirmed the close similarity in the neuropsychologic profiles of NLD and AS.

ABSTRACT

Autism is thought to be associated with abnormal hemispheric specialization and left-hemispheric dysfunction. Brain functional imaging using 133Xe-SPECT (single photon emission computed tomography) was used to measure left/right asymmetry and absolute values of regional cerebral blood flow (rCBF) in 18 children with autism aged from four to 17 years and 10 age-matched controls. All controls but only 10 children with autism were right-handed. The left-to-right indices, both hemispheric and regional, were positive in controls, indicating higher left than right rCBF values, but were negative in patients with autism. This inversion was statically significant for total hemispheres, sensorimotor and language-related cortex and was explained by a significant decrease of the left absolute rCBF values in these regions in the patients with autism. The inversion was independent of handedness, sex and age. These results confirm the existence of left-hemispheric dysfunction in childhood autism, especially in the cortical areas devoted to language and handedness, leading to anomalous hemispheric specialization.

Abstract: Disturbances in lateral preference in autism are of interest because of their potential to shed light on brain maturational processes in this disorder. Forty-seven autistic individuals with a history of disordered early language development and 22 autistic individuals with normal early language acquisition were matched with 112 healthy individuals and compared on a standardized measure of lateral preference, the Edinburgh Handedness Inventory. Autistic individuals with a history of early language disturbance showed more atypical cerebral dominance than both healthy participants and autistic individuals with normal early language skills. The data indicated maturational disturbances in establishing lateral preference rather than increased rates of left handedness. Atypical establishment of cerebral dominance may be one cause of disordered language development in autism.

Abstract: Two experiments involving listening preferences of autistic and normal subjects were conducted to test the hypothesis that the right cerebral hemisphere is more active than the left hemisphere in autistic children. Results showed that when given a choice between verbal and musical material, the autistic children preferred music, while normal children showed no preference. Secondly, autistic children listened to both types of material predominantly with the left ear. Although normal subjects showed greater variation among themselves, they tended to listen to music more often with the left ear and to listen to verbal material more often with the right. These results support the notion that some autistic children are predominantly right hemisphere processors.

Abstract: An fMRI study was used to measure the brain activation of a group of adults with high-functioning autism compared to a Full Scale and Verbal IQ and age-matched control group during an n-back working memory task with letters. The behavioral results showed comparable performance, but the fMRI results suggested that the normal controls might use verbal codes to perform the task, while the adults with autism might use visual codes. The control group demonstrated more activation in the left than the right parietal regions, whereas the autism group showed more right lateralized activation in the prefrontal and parietal regions. The autism group also had more activation than the control group in the posterior regions including inferior temporal and occipital regions. The analysis of functional connectivity yielded similar patterns for the two groups with different hemispheric correlations. The temporal profile of the activity in the prefrontal regions was more correlated with the left parietal regions for the control group, whereas it was more correlated with the right parietal regions for the autism group.

If the right brain (or parts thereof) is affected in AS, then this side must involve socialization or something visual/spatial, or even both.

Extralinguistic Deficits

Again, RHD patients are unlikely to display the kinds of phonological, syntactic or semantic problems associated with aphasia. However, although they do not typically have many specific language problems, they definitely have difficulty communicating. This impairment seems to follow from an inability to integrate information; RHD patients apparently do not make adequate use of context in their interpretations of linguistic or nonlinguistic messages. They have difficulty distinguishing significant from unimportant information. For example a patient of mine when asked to describe the "Cookie Theft" picture card from the Boston focused on irrelevant features without describing the overall picture. Some aphasics with typical left hemisphere lesions present with executive function disturbance similar to right hemisphere syndrome.

Literal Interpretations

RHD patients may be able to comprehend only the literal meaning of language. Thus, they will often fail to understand many jokes, metaphors, irony, sarcasm, and common sayings that include figurative language. For example, if an RHD patient hears someone say that they are about to "hit the ceiling," he might assume that the person is really about to begin striking the ceiling. Such a patient may also have trouble understanding indirect requests. For example, if he is asked if he "could open the window," he may fail to identify this as a polite request and simply answer "yes" rather than opening the window.

These problems with figurative language may be viewed as one manifestation of the inability to base interpretations on context.

Difficulty identifying relevant information

When listening to a conversation or reading, an RHD patient may fail to abstract the main point contained in the information being shared. This happens in spite of the fact that, unlike an aphasic, the patient can understand all the individual words and grammatical structures used. For RHD patients, it appears that their comprehension of everyday language is impaired by a failure to distinguish important information from irrelevant detail and also by an inability to integrate According to Blake 2007, RH patients have difficulty comprehending non-literal language, humor, and multiple interpretations Furthermore, Blake says that their difficulty with language production includes: impulsivity, inefficiency, and egocentricity. She also says that the same problems are seen in traumatic brain injury.

Inability to interpret body language and facial expressions

In a conversation, RHD may miss out on important cues that should tell them about the emotional state and true intention of the person with whom they are interacting. This inability to interpret body language and facial expression may be related to an overall failure to use context in the interpretation of individual pieces of information. Problems with the interpretation of facial expression may also be due to the fact that RHD patients often fail to maintain eye contact with their conversation partners.

Flat affect

RHD patients may fail to display a wide range of facial expressions themselves. Also their speech is frequently aprosodic, or lacking variations in pitch and stress. Some patients will sound "robot-like," and thus be unable to express emotion or changes in meaning via changes in intonation. These patients will no longer be able to vary pitch to signal the difference between a question and a statement or use word stress changes within a sentence to signal a difference in meaning.

Problems with Conversational Rules

RHD patients may fail to follow conversational rules, including those governing turn-taking, the initiation and closure of a conversation. RHD patients may tend to dominate conversations, as they are frequently verbose. They may also fail to properly estimate levels of shared knowledge, failing to give the listener enough background information to understand their statements. According to Myers and Mackisack (1990), RHD patients appear to not care about the needs of the listener. They, like children in an early developmental phase, may assume too much knowledge on the part of the listener; or not enough. They appear to answer without adequate search for the right answer. They also may fail to pick up on non verbal cues that signal listener's reactions.

Impulsivity

RHD patients may exhibit poor judgment and problem solving abilities. They may require constant supervision due to a tendency to attempt tasks of which they are no longer physically capable. This may be related to anosognosia. They may also exhibit impulsivity in the sense of failing to censor the statements they make to other people.

Confabulation

RHD patients may make untrue statements. These do not usually seem to be deliberate lies. According to Brownwell et al. (1995), this may be the patient's way of responding to his own confusion rather than attempts to mislead the listener

RHD patients may occasionally have hallucinations.

Nonlinguistic Deficits

Disorientation to Time and Direction

RHD patients may exhibit disorientation to time and and direction. They are usually oriented to person and to place, however. Many hospital patients are somewhat disoriented to time. They may be unable to give the date, time of day, or day of the week accurately. Note that it is important to be reasonable when assessing orientation. It is perfectly normal to miss the day of the week or date by one day and such errors should not be taken as an indication that the patient is disoriented. Sometimes when I am on vacation I may not know the day or the date. We shouldn't expect more of our patients.

RHD patients may also have difficulty following directions or finding their way around a building. They will know where they are in a general sense (e.g., in the hospital), but have trouble finding their way to specific locations (e.g., the dining room).

This deficit, known as topological disorientation, is a product of their general inability to process spatial information. Some patients with left hemisphere parietal lobe lesions have similar problems

Left side neglect

Neglect is a syndrome in which the patient fails to recognize one side of the body and the environmental space surrounding this side of the body in the absence of paralysis and visual problems. Neglect is considered a deficit in directed attention. This means that patients demonstrate an inability to be aware of stimuli, attend to stimuli or recognize the significance of stimuli. Neglect may also be described as the inability to orient to stimuli with the purpose of acting upon them. According to Myers (1994, in Chapey,1994), although neglect may occur with left hemisphere damage (LHD) it is more severe, longer lasting and common with RHD. It can occur with frontal, temporal, and parietal lobe lesions as well as with some sub-cortical lesions ( Myers, 1994).

Patients with neglect may fail to eat food on the left side of their plates, begin reading in the middle of sentences and in other ways seem to completely ignore the neglected side. Some may even cease to identify their left side as part of their own bodies. RHD patients have been known to give their paralyzed left arms names like "the baby" or "the dead one." They might also request that someone remove the other person from their bed, referring to their left side. RHD patients with left neglect may also have difficulty with left side detail in visuo-constructional tasks. For example, if drawing a picture or building a model, they might leave out details on the left side. The severity of neglect is usually an indication of the size of lesion and the overall severity of the patient's condition.

Note that RHD patients may have visual deficits including left hemianopsia. This may occur along with neglect or might exist alone and be mistaken for neglect. Scanning behavior may be used to differentiate between left neglect and left hemianopsia. A patient who has hemianopsia without neglect will have difficulty seeing things in his left visual field, but will not ignore his left side. For this reason, such a patient may be observed turning his head to scan the left visual field. On the other hand, a patient who does have neglect will generally make few or no spontaneous efforts to look at things in the left area of his visual field. According to Myers (1994), most theories of neglect consider it a deficit in attention.

At this time, the site of lesion that causes neglect is not known. However, the syndrome is frequently associated with parietal lobe lesions.

As mentioned above, right side neglect does sometimes occur in patients with left hemisphere damage. However, it is fairly uncommon. (Right side neglect occurs in approximately twenty percent of patients with left hemisphere damage.) It is also less severe and usually of shorter duration than left side neglect.

Anosognosia

This term first used by Babinski is the failure to recognize the symptoms of one's own illness. RHD patients may deny that they have had a stroke. They may appear to be unaware of their hemiplegia or their cognitive deficits (Love and Webb, 2001). It is not uncommon for right hemisphere patients to state that they are perfectly capable of walking, driving and returning to work immediately despite all evidence to the contrary. Anosognosia may be described as severe denial. The source of this denial appears to be cognitive rather than emotional; it seems as though patients are unable rather than unwilling to recognize their deficits.

Because RHD patients do not fully comprehend the extent of their impairment, they are frequently less depressed than those with left hemisphere damage. This type of executive function difficulty can also appear in aphasic patients with left hemisphere lesions.

Visuospatial Deficits

RHD patients have difficulty processing many types of visual stimuli. These problems are apparently due to an inability to integrate information. RHD patients have trouble with figure-ground problems, recall of visual forms and mental rotation, or the ability to imagine how a figure would look if its orientation in space were changed. Constructional apraxia can also be present in patients with RHD. Their drawings tend to be scattered, fragmented, and spatially disorganized (Myers, 1994, in Chapey, 1994). According to Swindell (1988, in Myers, 1994), the drawings of RHD patients may not benefit from a model or from cueing and are not likely to improve over time.

Prosopagnosia, or the inability to recognize familiar faces, is one of the most striking visuospatial processing deficits manifested by RHD patients. This does not represent a difficulty with vision itself. A patient with prosopagnosia is able to describe the features of familiar faces, including eye and hair color, type of nose, etc. An artistic patient will even be able to draw the faces of family members and friends accurately yet be unable to recognize them. Rather, the problem seems to be related to the integration of visual perceptions and their association with information stored in memory. According to Love and Webb (2001), patients with this disorder usually have lesions in the right occipital-temporal lobe region. Color agnosia is often seen with prosopagnosia.

Abstract: Recent studies of ADHD implicate well-defined neuroanatomical networks and neurochemical pathways in its pathophysiological basis. Considerable attention has focused on the role of anterior and superior frontal regions and portions of the basal ganglia, including the caudate nucleus and globus pallidus. This paper reviews a growing literature suggesting differential involvement of right hemisphere mechanisms specialized for behavioral regulation and attention. Supportive data are drawn from neuropsychology, neuroanatomy, and neurochemistry. In addition, three cases are presented that illustrate the complex role of right hemisphere dysfunction in adult manifestations of ADHD. We suggest that the pleomorphic presentations of ADHD can be understood in terms of a spectrum of disturbances in overlapping neural regions, especially involving frontal and parietal areas of the right hemisphere and their connections to subcortical structures (including the striatum, limbic system and diencephalic nuclei).

The author describes 15 children with behavioral disturbances, a characteristic neuropsychological profile, and neurological findings consistent with right-hemisphere damage or dysfunction. Almost all of the children had attention deficit disorder. Some were obtuse or unable to interpret social cues, others could not express their feelings but appeared to be sensitive and aware of the emotions of others. The older children were generally in psychotherapy or counseling but responded poorly, suggesting that a different approach to treatment may be indicated.

Abstract

The authors present the case of an adult woman who was treated in the mental health system for many years for a syndrome of mixed anxiety and depression unresponsive to psychopharmacologic or psychotherapeutic treatment. A computed tomography scan revealed asymmetrical enlargement of the right temporal horn. This finding, as well as findings of severe difficulties in spatial relations together with mildly abnormal posturing of the left hand when walking (especially when the gait was stressed), suggested that the patient had a developmental disability of the right cerebral hemisphere. The authors conclude that because such patients might appear to have primarily psychiatric rather than neurologic problems, the diagnosis of right hemisphere dysfunction should be considered when the clinical presentation is indicative of atypical anxiety and affective disorders.

Abstract

Five right-handed patients (aged 45 to 78 years) developed acute psychotic disturbances in conjunction with infarcts in the right hemisphere. Their presentation was marked by agitation, inattention, suspiciousness, paranoid delusions, hallucinations, and lack of appropriate concern. Several of these patients initially received primary psychiatric diagnoses. Although neurological findings indicative of right hemisphere involvement could also be elicited, these were generally overshadowed by the more dramatic behavioral alterations. The electroencephalogram and computerized axial tomography were positive in most cases. These cases demonstrate that the possibility of a right hemisphere lesion needs to be entertained in patients who present with an atypical psychotic episode.

Autism affects the left hemisphere and AS affects the right hemisphere of the brain.